In the field of silver halide photographic materials, the so-called color diffusion transfer process in which diffusible dyes are imagewise formed followed by fixing them on an image receiving material is well known, and many proposals have been made for the process. In these processes, diffusible dyes are generally formed upon development of silver halides from compounds enhanced in nondiffusibility which are derived from image forming dyes colored beforehand (preformed dyes) (The compounds enhanced in nondiffusibility are hereinafter referred to as "coloring materials"). In such processes, addition of the coloring materials to silver halide emulsion layers causes undesirable sensitivity decrease to exposure, because of the filter effect due to the dye moieties of the coloring materials. As a means of avoiding this problem, the coloring materials for forming images are therefore added to layers far from the surfaces of the silver halide emulsion layers to be exposed to light in general. Although the sensitivity decrease due to the above-mentioned filter effect can be avoided by this means, long physical distances between the silver halide emulsions and the coloring materials from which diffusible dyes are formed result in nonefficient development information transfer to develop a defect in this process.
To overcome these problems, a so-called coupling system has been proposed, in which image formation is performed by a coupling reaction of couplers with oxidation products of developing agents which are formed as results of the development of silver halides. An advantage of this system is that both the developing agents and the couplers are colorless to overcome the defect in the system utilizing the preformed dyes, and accordingly, the above system is preferable to the coloring materials utilizing the preformed dyes. Examples of this process are described in U.S. Pat. No. 4,469,773, JP-B-63-36487 (The term "JP-B" as used herein means an "examined Japanese patent publication"), etc.
Incorporation of the above-mentioned color developing agents of the coupling system into the photographic materials, however, brings about insufficient compatibility of expected storage stability with activity in the coupling reaction. In this system, both the color developing agents and couplers are desired to be nondiffusive in view of prevention of color amalgamation between silver halide emulsion layers having different spectral sensitivities. In the processes known previously, it has been difficult, however, to form diffusible dyes from the couplers and color developing agents both of which are nondiffusive.
Furthermore, the above-mentioned processes also have the disadvantage of developing undesirable stains with time, because the color developing agents unused on development spread throughout the receiving material owing to large diffusibility thereof.